Sound Designing with Prairies

Turn down any side street that leads through a residential area--what do you see? Lawns dotted with trees and flower beds. Though suburbanites manage their greenery with mowers and weed whackers and clippers, not grazing animals and wildfires, is it any wonder that early man settled on open grasslands (savanna hypothesis). Prairies provide sound experiences that will lure your audience back home--provided that you use wind textures, insect medleys, and inspiring birdsongs subtly to gently evoke the deep ecology that ties all of us to our native land.

Previously we learned about sound designing with the elements of nature: Winds, Thunder & Rain, Flowing Water, and Waves. We now build on what we have learned to include wildlife living in their native habitats, beginning with an overview.

The big picture

In simplest terms: the more sunlight that reaches the Earth’s surface the louder the music plays-- as long as the solar panels, or plants leaves, are present to harvest the sun’s energy and channel it into the bioacoustic system. In other words, Earth is a solar powered juke box, and the different world biomes, or types of ecological communities, may serve to represent the different genres of nature’s music. An 1891 Map of the World showing the distribution of Vegetation according to the Zones of Physical Climate tells us that this link between sunlight and plants has been long recognized.

Prairies are located at temperate latitudes, which means that the amount of sunlight powering the bioacoustic system varies widely throughout the year. Winter solstice is dark and quiet, with perhaps only the sounds of wind, often further dampened by snow. Summer solstice is light and loud--the dawn chorus of songbirds has reached its crescendo and the insect populations are adding strong medleys.
As sound designers we want to know which natural sound will trigger the targeted emotional response from our audience, but to do this, we must first understand why people listen in the first place.

All higher animals hear

Some species may be blind, but no higher animal species are deaf. Sound carries the news and initiates exploration: we hear something, look in that direction, move closer for a better look, then touch, smell, and often, finally taste.

The modern world, however, is so full of vibrations, that, frankly, the news overload is TMI. As all animal species continued to evolve, natural selection weeded out those individuals who failed to hear sounds that were useful and gave a distinct survival advantage to those individuals who did. Over time, each species came to hear differently. Human hearing has been shaped by the environment of our ancestors and the choices that they made. So in this sense, the curve below highlights an important evolutionary point--some sounds have more significance to our lives than others.

We can see from this curve that healthy human ears are relatively insensitive to low frequencies and supersensitive to the frequencies between 2.5-5 kHz which correspond to the resonant frequencies of the auditory canal. This begs the question: What occurred in this sensitive frequency range that helped our ancestors gain a survival advantage? And the companion question: Might that help us gain a survival advantage in sound design?

Before we begin our search of the natural world, let’s acknowledge that audiologists already have at least one good answer. This area of sensitive hearing corresponds with sounds important to human speech, such as the Es sound, and this allows us to recognize some words more easily than others. But we cannot end our search with what might seem like an obvious answer, because like the rest of the animal kingdom, we must first be inquisitively alive before we can engage in a conversation.

Here’s an experiment you can do in the studio. Mix together sounds, lots of them, both common, everyday sounds and wilderness sounds. In my experiment, I included frogs, toads, birds, monkeys, insects, even human voices and music. Then apply a very strong filter so that only those sounds between 2.5-5 kHz can be heard. (If you want, you can even tighten the bandwidth to 2-4 kHz, which is the bandwidth some researchers use.) What do you hear? In my experiment, only one sound remained--birdsong.

Why would our ancestors gain a survival advantage if they could detect faint birdsong? Could it be that our nomadic ancestors navigated towards food, water, and a long enough favorable season to raise their young, by listening to the birds? Consider this: Of all the environmental indicators of habitats prosperous for humans, the presence of a healthy songbird community ranks number one. No wonder nature albums featuring birdsongs remain top sellers.

Sound Designing with Prairie Birds

Assuming that our ears evolved to better hear birdsong, then we have a powerful design strategy to employ for motivating our audience. Play a beautiful birdsong. Do you want to design a place of human prosperity? Include plenty of diverse birdsong and calls. Would you like to naturally lead your audience to a destination? Use birdsong as a navigational beacon. Do you want to create a sudden sense of doom? Fade the birds out entirely.

The presence of birds in your sound design will linger, provocatively, in the minds of your listeners long after your production has ended. So, keep a good inventory of bird vocalizations, some to inspire, others to alarm, a few to lull, and more to forewarn. Birds are your muses, your messengers, your angels.

Prairie birds are as busy communicating as we are. Songs are most often delivered at dawn and dusk and are more structurally elaborate than calls, which are comparatively short and simple, serving to expeditiously sound an alarm or maintain position in a flock foraging in dense vegetation. There also exists a wide variety of other prairie bird sounds that do not come from vocal chords, such as the Brrrrrrr of skydives and quick pullouts, and growls produced by air sacs slowly deflating, and something that sounds like a popcorn popper that’s caused by rapid tail twitches. Your choices for sound design are surprisingly varied.

Birds communicate for many reasons: to establish territory, attract mates, maintain social relationships, distribute information about local events, and avoid predation, to name a few. Elaborate, passionate songs are often mating calls. These can come at a price if a predator lurks nearby. Many songbirds learn their song from their parents, and like human speech, show geographic variation, or dialects. A Western Meadowlark in Montana will not sound the same as one in nearby Saskatchewan or California. Sound designers need to be mindful to use only one dialect for each location; otherwise the overlap will sound as if two conversations are occurring instead of one.

The trick with Prairies is to use just the right amount of birdsong and at just the right time to regulate the audience’s mood between prosperity and poverty while at the same time remaining realistic. If it is dawn or dusk, use background choruses and just a few featured solo performances. If it is spring, then use lots bird activity with bravado, after all it’s usually only the males that sing and the day length has triggered a flood of testosterone into their blood stream. When summer arrives, mating is over and birdsongs fade almost completely until the fall, when matching day lengths to spring once again pump testosterone into the males and singing resumes, but weakly; mates do not respond, and this brief resurgence passes. Winter is the season of silence--only a few calls or none at all. During any season bird communications happen most often under calm atmospheric conditions, especially in the morning. Some birds sing often from places with prominent exposure to more efficiently broadcast their message. Other species sing from places of hiding. If you want to learn more about the behavior of each bird species there are numerous authorities online, most notably The Cornell Lab of Ornithology.

If the prairie setting looks diverse, in other words, if you see many different plants and landscape elements, it’s safe to include a wider variety of bird species than if the grass stretches to the horizon. You can find tips on how to match sounds to vegetation in How to Record Prairies (available in Prairies by Quiet Planet).

A not-to-be-missed prairie location is the treasured birder’s spot called a lek. Leks are places where members of the grouse family gather to perform their sensational songs and dance. Sage Grouse, Greater Prairie Chickens, Lesser Prairie Chickens, and Sharp-tailed Grouse. If you are looking for an opportunity to showcase the auditory wonder of the prairie, look no further.

Sound Designing with Winds

Prairies are frequently windy throughout the day and then calm at night. Wind reduces sound propagation by causing sound waves to scatter. This emphasizes the importance of dawn and dusk as periods of optimal communication for wildlife. To overcome this narrow window of opportunity, prairie songbirds such as the Western Meadowlark use both high amplitude and frequency modulation in their song structure to increase message recognition under windy conditions. And some, such as the Sage Grouse, have more than wind to contend with. The cold and dry atmospheric conditions common to the high altitude of their native sage-grassland habitat further reduce the distance that sound will travel. Sage Grouse employ a variety of dramatic wing flaps and inflate and then slowly deflate large throat sacks to create growling, popping, low frequency sounds that carry recognizably farther than typical bird vocalizations.

Because wind scatters sound and makes communication more difficult than under calm conditions, it effectively acts as a valve that controls the information flow. As the wind kicks up after sunrise, scattering the sound waves, wildlife communication begins to shutdown. Animals generally hold most communications until later, when the wind subsides and calm conditions once again prevail.

Because the wind blows during most daylight hours on the prairie, you will want to become familiar with the many kinds of winds. (Read Sound Designing with Winds, Part 1 and Part 2.) Grasses have the characteristic whipping sound created by slender stems and points--the prevailing pitch of the grass wind sound corresponds with the length of the grass stems. The longer the stem the lower the pitch, and conversely, the shorter the stem the higher the pitch. But prairies, while also known as grasslands, are far from just grasses. There’s often an ample mix of broadleaved herbaceous plants collectively referred to as forbs that will impart leaf rustles and the rattle of dried seed pods. To the untrained ear, the wind sounds of the forbs may be mistaken for wind-driven litter on city streets, especially over inexpensive speakers, and therefore, use these cautiously in your design.

A distant wind sounds differently on the prairie than it does in a forest, mainly because it can be heard for many miles, meaning, minutes before it can be felt. This starts as a deep roar similar to distant traffic, except that this roar often foretells the arrival of wind, and soon the grasses and forbs are swaying

Sound Designing with Fire

Native prairies are maintained naturally by a natural burning cycle of three to five years. They’re usually started by lightning strikes. Under this cycle, plants and animals survive because fires burn quickly and cooler than if additional fuel is allowed to accumulate due to ill-conceived fire control measures.

There are two basic kinds of native wildfires--fire under calm conditions and fires under windy conditions. Calm conditions produce a slow-advancing delicate fire. Windy conditions produce a fast-traveling roar. Because both of these fires sound differently than familiar campfires, the audience will likely not recognize this sound unless a strong context is created, such as preceding the wildfire sounds with a sizzling clap of thunder.

Know, too, that a wildfire’s rising plumes of smoke dramatically effect the passage of sound through them, similar to the sound-scattering effect of wind, but this quiet area above the fire changes quickly. The aural effect is similar to looking through turbulent water that can alternate clear and then blurred views of what lies below.

Sound Designing with Insects

Insects are the dominant prairie herbivore and quickly reach high population levels once the growing season provides a food base and temperatures increase. Insects are cold blooded, so as temperatures warm during the day, insects become audible through a variety of ways: humming caused by myriad of wings (the frequency of the hum matches the wing beats per second); the rubbing together of body parts (stridulation), as in crickets; and the clapping together of outer wing covers (crepitation), as when grasshoppers are in flight. The heat retaining properties of the earth can often facilitate insect activity well into the night, but as temperatures decrease, so will insect sounds, to none, until just before sunrise.

Insects are not fire resistant. It is interesting to note that Native Americans living on prairies would sometimes light fires for fly and mosquito control. Therefore, should a fire be included in a sound design, it would be prudent to reduce or remove the audible presence of insects.

Sound Designing with Ecotones

Much of the prairies region in North America were long ago overridden by glaciers, which, in retreating, produced potholes that remain today as lakes (prairie pothole region). So in some prairies, grasslands and wetlands share the acoustic environment, creating an ecotone, a place where two ecological communities intersect. Ecotone sound design can be very diverse and very musical, however, at very active times like spring breeding season, more sound that an audience can endure with interest. Use ecotones as needed, but be brief so as not to fatigue your audience’s attention.

Since prairies have been heavily tapped for other land uses, such as timber production, flood control, agriculture, (less than 2 percent of the original prairie remains), native prairies may contain complex ecotones made up of wetlands, riparian, and forest species. I find these complex ecotones confusing and suggest they be avoided.

Other Considerations

Several prairie species have had formative roles in shaping prairie life, such as the five species of prairie-dogs, two ecotypes of American bison, and black-footed ferret. As we would expect sound plays a significant role in their life history.

The Gunnison’s Prairie Dog exhibits one of the animal kingdom’s most sophisticated forms of communication. Its bark is a combination of one or two high-pitched audible syllables, with the second syllable lower and deeper. Eleven distinct warning calls can be heard by humans, but to a Gunnison’s Prairie Dog’s ear there are many more, for a single chirp can carry information such as who approaches, what color they wear, rate of travel, and whether they display threatening behavior.

The Gunnison’s Prairie Dog exhibits one of the animal kingdom’s most sophisticated forms of communication. Its bark is a combination of one or two high-pitched audible syllables, with the second syllable lower and deeper. Eleven distinct warning calls can be heard by humans, but to a Gunnison’s Prairie Dog’s ear there are many more, for a single chirp can carry information such as who approaches, what color they wear, rate of travel, and whether they display threatening behavior.

Summary

Prairies offer some of the most engaging sounds available to sound designers. Prairie birdsong is particularly rich in both amplitude and frequency modulation. Skillful use of birdsong, insects, winds, and other sounds can build effective and emotionally convincing sound designs that can lead your audience back to an ancient homeland.